Cambelt or chain — how do I know what I have?

Updated April 2026 · Diesel Automotive workshop notes

Belts and chains both keep the camshaft in time with the crankshaft, but they age differently and they cost very different amounts to replace. If you don't know which yours has, here's how to find out — and why it matters.

The simplest way to check

Send us your reg or VIN and we'll tell you within the working day. Or check:

• Owner's handbook — service section will say "timing belt" or "timing chain"
• Service history — a previous cambelt change would be itemised; a chain wouldn't appear unless replaced
• Manufacturer parts catalogue — searching your engine code (on the engine block) returns belt or chain parts
• Visual inspection — a plastic timing cover usually means belt; a heavier metal/oil-bathed cover usually means chain

Common belt engines (most diesels pre-2010)

• Ford 1.6 / 2.0 TDCi (Mondeo, Focus, Galaxy, Transit)
• Vauxhall 1.7 / 1.9 CDTi
• VAG 1.9 / 2.0 TDI 4-cyl (Golf, Passat, A3, A4, Octavia)
• Renault 1.5 dCi
• Peugeot/Citroën 1.6 HDi (and Ford 1.6 TDCi joint-venture variants)

These need replacing on the manufacturer interval — typically 60,000–100,000 miles, or 5–7 years.

Common chain engines (most diesels post-2010)

• BMW N47 / N57 / B47 (chain at the rear of the engine)
• Mercedes OM651 (also chain at the rear)
• VAG 2.5 / 3.0 TDI V6 (chain at the rear)
• Some Ford EcoBoost variants (wet-belt converted to chain on later spec)
• Newer Sprinter, Crafter, Vivaro chain platforms

These don't have a fixed mileage interval — they're replaced on symptoms (rattle on cold start, fault codes, stretched chain on diagnostic data) or as preventative maintenance at high mileage.

Why it matters

If you have a belt: budget for a planned replacement at the right interval. A snapped belt on most diesels means engine destruction — much more expensive than the £299–£499 fitted price for a proper cambelt job.

If you have a chain: keep an ear out for cold-start rattle. Don't ignore correlation fault codes. Chain replacement is more involved (and more expensive) than a belt — but ignoring chain wear leads to even more expensive damage. See our timing chain replacement page.